TY - JOUR

T1 - Microhydrological niches in soils

T2 - How mucilage and EPS alter the biophysical properties of the rhizosphere and other biological hotspots

AU - Benard, Pascal

AU - Zarebanadkouki, Mohsen

AU - Brax, Mathilde

AU - Kaltenbach, Robin

AU - Jerjen, Iwan

AU - Marone, Federica

AU - Couradeau, Estelle

AU - Felde, Vincent J.M.N.L.

AU - Kaestner, Anders

AU - Carminati, Andrea

N1 - Funding information: P. Benard was funded by the German Research Foundation (DFG CA921/8-1) and the Ministry for Science and Culture of Lower Saxony (VWZN 3152). Neutron imaging was conducted at ICON (Imaging with Cold Neutrons), and imaging of maize mucilage distribution in sand and glass beads was conducted at SLS (Swiss Lightsource) facility of the PSI, Switzerland. This research used resources of the Advanced Light Source, Beamline 8.3.2, which is a USDOE Office of Science User Facility (DE-AC02-05CH11231). This work was supported by a grant of the National Science Foundation (DEB-0717164), and by the USDOE Office of Science, and through the USDOE Office of Science, Office of Biological and Environmental Research Early Career Program under contract to Lawrence Berkeley National Laboratory (DE-AC02-05CH11231). E. Couradeau was funded from the European Union’s Seventh Framework Program for Research, Technological Development, and Demonstration (328530). This publication was funded by the German Research Foundation (DFG) and the University of Bayreuth in the funding programme Open Access Publishing.

PY - 2019

Y1 - 2019

N2 - Plant roots and bacteria are capable of buffering erratic fluctuations of water content in their local soil environment by releasing a diverse, highly polymeric blend of substances (e.g. extracellular polymeric substances [EPS] and mucilage). Although this concept is well accepted, the physical mechanisms by which EPS and mucilage interact with the soil matrix and determine the soil water dynamics remain unclear. High-resolution X-ray computed tomography revealed that upon drying in porous media, mucilage (from maize [Zea mays L.] roots) and EPS (from intact biocrusts) form filaments and two-dimensional interconnected structures spanning across multiple pores. Unlike water, these mucilage and EPS structures connecting soil particles did not break up upon drying, which is explained by the high viscosity and low surface tension of EPS and mucilage. Measurements of water retention and evaporation with soils mixed with seed mucilage show how these one-and two-dimensional pore-scale structures affect macroscopic hydraulic properties (i.e., they enhance water retention, preserve the continuity of the liquid phase in drying soils, and decrease vapor diffusivity and local drying rates). In conclusion, we propose that the release of viscous polymeric substances and the consequent creation of a network bridging the soil pore space represent a universal strategy of plants and bacteria to engineer their own soil microhydrological niches where stable conditions for life are preserved.

AB - Plant roots and bacteria are capable of buffering erratic fluctuations of water content in their local soil environment by releasing a diverse, highly polymeric blend of substances (e.g. extracellular polymeric substances [EPS] and mucilage). Although this concept is well accepted, the physical mechanisms by which EPS and mucilage interact with the soil matrix and determine the soil water dynamics remain unclear. High-resolution X-ray computed tomography revealed that upon drying in porous media, mucilage (from maize [Zea mays L.] roots) and EPS (from intact biocrusts) form filaments and two-dimensional interconnected structures spanning across multiple pores. Unlike water, these mucilage and EPS structures connecting soil particles did not break up upon drying, which is explained by the high viscosity and low surface tension of EPS and mucilage. Measurements of water retention and evaporation with soils mixed with seed mucilage show how these one-and two-dimensional pore-scale structures affect macroscopic hydraulic properties (i.e., they enhance water retention, preserve the continuity of the liquid phase in drying soils, and decrease vapor diffusivity and local drying rates). In conclusion, we propose that the release of viscous polymeric substances and the consequent creation of a network bridging the soil pore space represent a universal strategy of plants and bacteria to engineer their own soil microhydrological niches where stable conditions for life are preserved.

UR - http://www.scopus.com/inward/record.url?scp=85068940423&partnerID=8YFLogxK

U2 - 10.2136/vzj2018.12.0211

DO - 10.2136/vzj2018.12.0211

M3 - Article

AN - SCOPUS:85068940423

VL - 18

JO - Vadose zone journal

JF - Vadose zone journal

SN - 1539-1663

IS - 1

M1 - 180211

ER -